Cancer remains a major public health challenge despite progress in detection and therapy. Cancer cells are characterized by the production of cancer-associated marker proteins. Cancer-associated proteins are found both in the tissues and in the bodily fluids of an individual who carries cancer cells. Their levels usually are low at the early stages of the carcinogenic progress and increase during the disease's progression and only in rare cases proteins are observed showing a decreased level in the course of disease progression. The sensitive detection of these proteins is an advantageous and promising approach for the diagnosis of cancer, in particular in an early stage diagnosis of cancer. The most prevalent cancer types are breast cancer (BC), lung cancer (LC) and colorectal cancer (CRC).
The most important therapeutic approaches for solid tumors are:                a) surgical resection of the tumor,        b) chemotherapy,        c) radiation therapy,        d) treatment with biologicals, like anti-tumor antibodies or anti-angiogenic antibodies and        e) a combination of the above methods.        
Surgical resection of the tumors is widely accepted as a first line treatment for early stage solid tumors. Most cancers, however, are detected only when they become symptomatic, i.e., when patients already are in a rather late stage of disease progression.
The staging of cancer is the classification of the disease in terms of extent, progression, and severity. It groups cancer patients so that generalizations can be made about prognosis and the choice of therapy.
The different stages of CRC used to be classified according to Dukes' stages A to D. Today, the TNM system is the most widely used classification of the anatomical extent of cancer. It represents an internationally accepted, uniform staging system. There are three basic variables: T (the extent of the primary tumor), N (the status of regional lymph nodes) and M (the presence or absence of distant metastases). The TNM criteria are published by the UICC (International Union Against Cancer), Sobin, L. H., Wittekind, Ch. (eds.), TNM Classification of Malignant Tumours, sixth edition (2002)). Once the TNM status is determined the patients are grouped into disease stages that are denoted by Roman numerals ranging form I to IV with IV being the most advanced disease stage. TNM staging and UICC disease stages correspond to each other as shown in the following table taken from Sobin and Wittekind (eds.), supra.
TABLE 1Interrelation of TNM staging and UICC disease stagesUICC disease stageT stagingN stagingM stagingStage 0TisN0M0Stage IT1, T2N0M0Stage IIAT3N0M0Stage IIBT4N0M0Stage IIIAT1, T2N1M0Stage IIIBT3, T4N1M0Stage IIICAny TN2M0Stage IVAny TAny NM1
What is especially important is that early diagnosis cancer, e.g., of CRC translates to a much better prognosis. In CRC malignant tumors of the colorectum arise from benign tumors, i.e., from adenoma. Therefore, best prognosis have those patients diagnosed at the adenoma stage. Patients diagnosed as early as in stage Tis, N0, M0 or T1-3; N0; M0, if treated properly have a more than 90% chance of survival 5 years after diagnosis as compared to a 5-years survival rate of only 10% for patients diagnosed when distant metastases are already present.
Current detection methods including imaging methods, such as X-ray or nuclear resonance imaging in theory might at least partially be appropriate for use as a general screening tool. However, they are very costly and not affordable to health care systems for a general and broad use in mass screenings of large numbers of subjects, particularly for subjects without any tumor symptoms.
Thus, it is an object of the present invention to provide a simple and cost-efficient procedure of tumor assessments, e.g., to identify individuals suspect of having cancer. For this purpose, a general tumor marker which is detectable in body fluids, e.g., blood or serum or plasma or a panel of such markers, would be desirable.
A number of serum tumor markers are already in clinical use. For example the soluble 30 kDa fragment of cytoceratin 19 (CYFRA 21-1), carcinoembryogenic antigen (CEA), neuron-specific enolase (NSE), and squamous cell carcinoma antigen (SCC) are the most prominent LC markers. However, none of them meets the criteria for sensitivity and specificity required for a screening tool (Thomas, L., Labor and Diagnose, T H Books Verlagsgesellschaft, Frankfurt/Main, Germany (2000)).
In order to be of clinical utility, a new diagnostic marker as a single marker should be comparable to other markers known in the art, or better. Or, a new marker should lead to a progress in diagnostic sensitivity and/or specificity either if used alone or in combination with one or more other markers, respectively. The diagnostic sensitivity and/or specificity of a test is best assessed by its receiver-operating characteristics, which will be described in detail below.
Whole blood, serum or plasma are the most widely used sources of sample in clinical routine. The identification of an early tumor marker that would aid in the reliable cancer detection or provide early prognostic information could lead to a method that would greatly aid in the diagnosis and in the management of this disease. Therefore, an urgent clinical need exists to improve the in vitro assessment of cancer and in particular of LC. It is especially important to improve the early diagnosis of cancer, e.g., LC, since for patients diagnosed early on chances of survival are much higher as compared to those diagnosed at a progressed stage of disease.
The clinical utility of biochemical markers in lung cancer has recently been reviewed (Duffy, M. J., Crit. Rev. Clin. Lab. Sci. 38 (2001) 225-262).
CYFRA 21-1 is currently regarded to be the best of the presently known tumor markers for lung cancer. Even though not organ-specific it is predominantly found in lung tissue. Sensitivity of CYFRA 21-1 for lung cancer is described to be between 46-61% at a specificity of 95% towards other benign lung diseases. Increased serum levels of CYFRA 21-1 are also associated with pronounced benign liver diseases, renal insufficiency and invasive bladder cancer. CYFRA 21-1 testing is recommended for postoperative therapy surveillance.
CEA belongs to the group of carcinofetal antigens, usually produced during embryogenesis. CEA is not organ-specific and predominantly used for monitoring of colorectal cancer. Besides malignancies, also several benign diseases such as cirrhosis, bronchitis, pancreatitis and autoimmune diseases are associated with increased CEA serum levels. At 95% specificity towards benign lung diseases its sensitivity for lung cancer is reported to be 29-44%. The primary use of CEA is in monitoring colon cancer, especially when the disease has metastasized. However, a variety of cancers can produce elevated levels of CEA, including breast cancer. A preferred use of CEA is therapy surveillance of lung cancer.
NSE is a tumor marker for SCLC. Generally, increased NSE serum levels are found in association with neuroectodermal and neuroendocrine tumors. Increased serum levels are also found in patients with benign lung diseases and cerebral diseases, such as meningitis or other inflammatory diseases of the brain, and traumatic injuries to the head. While sensitivity for SCLC at 95% specificity is reported to be 60-87%, performance of NSE testing for NSCLC is poor (7-25%). NSE is recommended for therapy surveillance of SCLC.
CA 19-9 (carbohydrate antigen 19-9), a sialylated Lewis (a) antigen) on a glycolipid is a tumor marker for gastrointestinal cancers. It occurs in fetal gastric, intestinal and pancreatic epithelia. Low concentrations can also be found in adult tissue in the liver, lungs, and pancreas. There is no correlation between tumor mass and the CA 19-9 assay values Therefore the determination of CA 19-9 cannot be used for the early detection of pancreatic carcinoma. As the mucin is excreted exclusively via the liver, even slight cholestasis can lead to clearly elevated CA 19-9 serum levels in some cases. The marker is mainly used as an aid in the monitoring of disease status in those patients having confirmed pancreatic cancer (sensitivity 70-87%). 3-7% of the population have the Lewis a-negative/b-negative blood group configuration and are unable to express the mucin with the reactive determinant CA 19-9. This must be taken into account when interpreting the findings.
CA 125 is found in a high percentage of non-mucinous ovarian tumors of epithelial origin and can be detected in serum. Ovarian carcinoma accounts for about 20% of gynecological tumors. Although the highest CA 125 values occur in patients suffering from ovarian carcinoma, clearly elevated values are also observed in malignancies of the endometrium, breast, gastrointestinal tract, and various other malignancies. Increased values are sometimes found in various benign gynecological diseases such as ovarian cysts, ovarian metaplasia, endometriosis, uterus myomatosus or cervicitis. Slight elevations of this marker may also occur in early pregnancy and in various benign diseases (e.g., acute and chronic pancreatitis, benign gastrointestinal diseases, renal insufficiency, autoimmune diseases and others). Markedly elevated levels have been found in benign liver diseases such as cirrhosis and hepatitis. Extreme elevations can occur in any kind of ascites due to malignant and benign diseases. Although CA 125 is a relatively unspecific marker, it is today the most important tumor marker for monitoring the therapy and progress of patients with serous ovarian carcinoma. A sensitivity of 69-79% is reported for 82-93% specificity.
PSA (“prostate related antigen”) is commonly tested tumor marker used in blood testing. PSA appears to have a high tissue specificity; the glycoprotein is found in normal prostatic epithelium and secretions but not in other tissues. PSA is highly sensitive for the presence of prostatic cancer. The elevation correlated with stage and tumor volume. It is predictive of recurrence and response to treatment. Finally, the antigen has prognostic value in patients with very high values prior to surgery are likely to relapse.
NNMT (nicotinamide N-methyltransferase; Swiss-PROT: P40261) has an apparent molecular weight of 29.6 kDa and an isoelectric point of 5.56. NNMT catalyzes the N-methylation of nicotinamide and other pyridines. This activity is important for biotransformation of many drugs and xenobiotic compounds. The protein has been reported to be predominantly expressed in liver and is located in the cytoplasm. NNMT has been cloned from cDNA from human liver and contained a 792-nucleotide open reading frame that encoded a 264-amino acid protein with a calculated molecular mass of 29.6 kDa (Aksoy, S. et al., J. Biol. Chem. 269 (1994) 14835-14840). Little is known in the literature about a potential role of the enzyme in human cancer. In one paper, increased hepatic NNMT enzymatic activity was reported as a marker for cancer cachexia in mice (Okamura, A. et al., Jpn. J. Cancer Res. 89 (1998) 649-656). In a recent report, down-regulation of the NNMT gene in response to radiation in radiation sensitive cell lines was demonstrated (Kassem, H. S. et al., Int. J. Cancer 101 (2002) 454-460). It has recently been found (WO 2004/057336) that NNMT will be of interest in the assessment of CRC.
ProGRP is a tumor marker, useful in the detection and monitoring of SCLC. Increased serum levels are also found in patients with nonmalignant lung/pleural diseases, such as idiopathic pulmonary fibrosis or sarcoidosis. While sensitivity for proGRP in the field of SCLC (at 95% specificity) is reported to be 47-86%, the performance of proGRP testing in the field of NSCLC is poor because the sensitivity is reported as being below 10%).
SCC was originally identified in squamous cell CA of the cervix. The sensitivity of SCC for LC in general is low (18-27%). Therefore, SCC testing is regarded to be not suitable for screening. However, due to a higher sensitivity for squamous cell CA, a preferred use for SCC is therapy surveillance, even though CYFRA 21-1 generally performs better.
p53 (TP53, cellular tumor antigen p53, tumor suppressor p53 or phosphoprotein p53) is a transcription factor inducing cell growth arrest or apoptosis (Appella, E. et al., Pathol. Biol. 48 (2000) 227-245). p53 acts as a tumor suppressor in many tumor types and inactivating mutations in its gene are the most common genetic events promoting cancer development in humans (reviewed in Olivier, M. and Petitjean, A., Cancer Gene Ther. 16 (2009) 1-12; Petitjean, A. et al., Oncogene 26 (2007) 2157-2165). p53 mutation is observed in 40-50% of colorectal carcinomas, and is associated with carcinoma aggressiveness (Soussi, T., Cancer Res. 60 (2000) 1777-1788). Mutations in p53 gene lead not only to the disruption of the protein function, but also to the expression of tumor-associated antigens (TAA) and initiation of the autoimmune response and generation of specific anti-p53 autoantibodies in sera of cancer patients (Zhang, J. Y. et al., Cancer Epidemiology, Biomarkers & Prevention 12 (2003) 136-143; Soussi, T., Cancer Res. 60 (2000) 1777-1788). Detection of anti-p53 autoantibodies in human sera is an emerging tool for the diagnosis and management of cancer. Dependent of the cancer type, the frequency of anti-p53 autoantibodies in sera range from 17.8% (CRC) to 16.1% (LC) and 7.8% (Breast Cancer) (Tan, E. M. and Zhang, J., Immunological Reviews 222 (2008) 328-340; Zhang, J. Y. et al., Cancer Epidemiology, Biomarkers & Prevention 12 (2003) 136-143).
Seprase, also known as fibroblast activation protein (FAP), is as a 170 kDa glycoprotein having gelatinase and dipeptidyl peptidase activity consisting of two identical monomeric seprase units (Pineiro-Sanchez, M. L. et al., J. Biol. Chem. 272 (1997) 7595-7601; Park, J. E. et al., J. Biol. Chem. 274 (1999) 36505-36512). The monomer of the human membrane bound seprase protein comprises 760 amino acids. Human seprase is predicted to have its first 4 N-terminal residues within the fibroblast cytoplasm, followed by a 21-residue transmembrane domain and then a 734 residue extracellular C-terminal catalytic domain (Goldstein et al., Biochim Biophys Acta. 1361 (1997) 11-19; Scanlan, M. J. et al., Proc Natl Acad Sci USA 91 (1994) 5657-5661). A shorter form of human seprase protein is known to a person skilled in the art as soluble seprase or circulating antiplasmin-cleaving enzyme (APCE) (Lee, K. N. et al., Blood 103 (2004) 3783-3788; Lee, K. N. et al., Blood 107 (2006) 1397-1404), comprising the amino acid positions 26-760 from Swissprot database Accession number Q12884. The dimer of soluble seprase is a 160 kDa glycoprotein consisting of two identical monomeric soluble seprase protein units. Piñeiro-Sánchez et al. (supra) found that a increased expression of seprase correlates with the invasive phenotype of human melanoma and carcinoma cells. Henry, L. R. et al., Clin. Cancer Res. 13 (2007) 1736-1741 describe that human colon tumor patients having high levels of stromal seprase are more likely to have aggressive disease progression and potential development of metastases or recurrence.
Human dipeptidyl peptidase IV (DPPIV), which is also known as CD26, is a 110 kDa cell surface molecule. The amino acid sequence of human DPPIV protein comprises 766 amino acids. It contains intrinsic dipeptidyl peptidase IV activity which selectively removes N-terminal dipeptide from peptides with proline or alanine in the third amino acid position. It interacts with various extracellular molecules and is also involved in intracellular signal transduction cascades. The multifunctional activities of human DPPIV are dependent on cell type and intracellular or extracellular conditions that influence its role as a proteolytic enzyme, cell surface receptor, co-stimulatory interacting protein and signal transduction mediator. Human DPPIV has a short cytoplasmatic domain from amino acid position 1 to 6, a transmembrane region from amino acid position 7 to 28, and an extracellular domain from amino acid position 29 to 766 with intrinsic dipeptidyl peptidase IV (DPPIV) activity. Human soluble dipeptidyl peptidase IV (soluble DPPIV) comprises the amino acid positions 29 to 766 from Swissprot database Accession number P27487. The dimer of soluble DPPIV is a 170 kDa glycoprotein consisting of two identical monomeric soluble DPPIV units.
Soluble DPPIV/seprase complex (DPPIV/seprase) refers to the soluble complex formed of a soluble DPPIV homodimer (170 kDa) and a soluble seprase homodimer (160 kDa) with a molecular weight of 330 kDa. Under certain conditions this complex may form a double complex having a molecular weight of 660 kDa.
With respect to marker profiles and aiming at improved diagnosis of lung cancer, a method was published (Schneider, J. et al., Int. J. Clin. Oncol. 7 (2002) 145-151) using fuzzy logic based classification algorithms to combine serum levels of CYFRA 21-1, NSE and C-reactive protein (CRP) which is a general inflammation marker. The authors report a sensitivity of 92% at a specificity of 95%. However in this study, for example the sensitivity of CYFRA 21-1 as a single tumor marker is reported to be at 72% at a specificity of 95%, which is significantly higher than in many other reported studies. Duffy, M. J., in Crit. Rev. Clin. Lab. Sci. 38 (2001) 225-262, report a sensitivity of between 46% and 61%. This unusual high performance achieved by Schneider et al., raises some doubts and might be due to several facts. Firstly, the collective of control patients seems to be younger than the patients collective, i.e., the groups are not well age-matched, and the patient collective comprises many late stages. Secondly and even more critical, the performance of the algorithm is checked on the samples of the training set which were used for the determination of the fuzzy logic qualifiers. Hence, these qualifiers are strictly speaking “tailor-made” for this set and not applied to an independent validation set. Under normal circumstances, is has to be expected that the same algorithm applied to a larger, independent, and well balanced validation set will lead to a significantly reduced overall performance.
It was the object of the present invention to investigate whether a biochemical marker can be identified which may be used in assessing cancer disease. In particular, the inventors of the present invention investigated whether a biochemical marker could be identified for the assessment of different cancer types, such as lung, breast, colon, prostate and kidney cancer in body fluids. In a very preferred aspect of the present invention, the identification of a biochemical marker for the assessment of lung cancer (LC) was investigated.
Surprisingly, it has been found that use of secernin-1 protein (SCRN1) can at least partially overcome some of the problems of the markers presently known in the state of the art.
Surprisingly, it has been found that a increased concentration of SCRN1 in the test sample is associated with the occurrence of cancer. It could be shown that SCRN1 is a marker which is not specific for a single type of cancer, but a marker for different types of cancer, i.e., a general tumor marker. Since SCRN1 appears to be rather specific for tumorigenic processes, the novel tumor marker SCRN1 has great potential to be of clinical utility with various classes of tumor types.
Surprisingly, it was found in the present invention that a determination of the concentration of SCRN1 in a sample and/or body fluid, allows the assessment of cancer, e.g., of lung, ovary, endometrium, melanoma, breast, head and neck, bladder, pancreas, colon, cervix, kidney or prostate cancer. Even more surprisingly, it was found that a increased concentration of SCRN1 or fragments thereof in a sample and/or body fluid compared to normal controls is indicative for the risk or occurrence of cancer.
The present invention relates to a method for assessing cancer in vitro comprising measuring in a sample the concentration of SCRN1 by an immunological detection method and using the measurement result, particularly the concentration determined, in the assessment of cancer.